Clustering is a mechanism that enables multiple processes and programs to work together as one entity. For example, when you go to google.com and search for something, it may seem like your search request is processed by only one web server. In reality, your search request is processed by thousands of web servers connected in a cluster. Similarly, you can have multiple instances of the OpenDaylight controller working together as one entity. There are a number of uses for clustering:
- Scaling: If you have multiple controllers running, you can potentially do more work with or store more data on those controllers if they are clustered. You can also break up your data into smaller chunks (known as shards) and either distribute that data across the cluster or perform certain operations on certain members of the cluster.
- High Availability: If you have multiple controllers running and one of them crashes, you would still have the other instances working and available.
- Data Persistence: You will not lose any data gathered by your controller after a manual restart or a crash.
The following sections describe how to set up clustering on both individual and multiple OpenDaylight controllers.
